This application relates to and incorporates by reference Japanese patent application no. 2001-126467 filed on Apr. 24, 2001 and Japanese patent application no. 2001-362453 filed on Nov. 28, 2001
This invention relates to a compressor with a complex drive system adapted to drive the compressor such that the compressor is rotated selectively by either of a main drive source, such as an internal combustion engine, and an electric motor, which is rotated by a power source such as a battery.
An idle-stop system, which completely stops the internal combustion engine of an automobile when the automobile stops, has been developed in recent years to reduce fuel consumption. However, passengers feel uncomfortable when the automobile stops, because the compressor of the air conditioning system, which is driven by the internal combustion engine, stops operating when the engine stops. This problem can be avoided by using a so called hybrid compressor, which is driven selectively by two power sources, such that the compressor is driven by the electric power stored in a battery when the internal combustion engine is stopped.
Japanese unexamined patent publication Hei. 11-287182 discloses such a hybrid compressor. In this publication, a pulley is fitted to and interlocked with the drive shaft of the compressor by an electromagnetic clutch so that the compressor may be rotated by the internal combustion engine through a belt, and an electric motor, which is driven by a battery, is fitted to the same drive shaft. This is a common arrangement for driving a compressor selectively with two power sources. The electric motor is provided with a power generating function that employs the internal combustion engine as drive source. The compressor is a variable capacity type compressor, and the power generating function is used only when the discharge capacity falls below a predetermined level. More specifically, the electric power generated by the driving force of the internal combustion engine is controlled by a controller to be inversely proportional to the discharge capacity of the compressor. The electric motor has a known configuration and includes a rotor that rotates with its drive shaft (armature) and a stator arranged around the outer periphery of the rotor and rigidly secured to the housing (field system).
With the arrangement described in the above cited publication, the load of the internal combustion engine is prevented from rising dramatically, and the efficiency of energy use of the vehicle is improved, since power is supplied to the compressor in a manner that supports the air conditioning function of the vehicle, because the electric power generation load is eliminated when the compressor load on the internal combustion engine exceeds a certain level.
However, electricity is generated whenever the rotor of the electric motor is driven by the internal combustion engine and the electric motor is forced to produce a high voltage when the electric power generating function is suspended (and the electric path between the electric motor and the battery is blocked) by the control section. Therefore, the insulators and other elements in the electric motor need to be provided with measures that make them withstand a high voltage that may be applied to them, which increases the cost of manufacturing the electric motor. Additionally, when the rotor of the electric motor is driven, a core loss arises as a function of the generated electric current. Thus, the internal combustion engine is forced to consume energy necessary for generating electricity and also for compensating the core loss.
In view of the above identified problems of the prior art, it is therefore an object of the present invention to provide a complex drive system for a compressor that prevents the power generating function of the electric motor from operating when the internal combustion engine is in operation, which makes it unnecessary to provide the electric motor with a structure for withstanding high voltage and reduces the load on the internal combustion engine.
In a first aspect of the present invention, the above object is achieved by providing a compressor with a complex drive system. The drive system includes a pulley to be driven by a main, or first, source and an electric motor, or second drive source, powered by a power source. The motor has an armature and a field system. The drive system operates the compressor by selectively using the pulley and the electric motor. The armature and the field system of the electric motor are rotatable and independently supported. The pulley is mechanically connected to either of the armature and the field system, and the compressor is mechanically connected to the other of the field system and the armature. The system further includes an interlocking device between the armature and the field system for interlocking the pulley and the compressor to make the compressor follow the rotary motion of the pulley.
When the main, or first, drive source, which is typically an internal combustion engine, is operating, the driving force of the first drive source is transmitted to either of the armature and the field system from the pulley. Then, the drive force is further transmitted to the other of the armature and the field system by the interlocking device. Since the armature and the field system are driven synchronously, the electric motor is prevented from generating electric power while the first drive source is in operation so that no high voltage will be produced in the electric motor. Therefore, insulators and other elements in the electric motor do not need to be provided with measures that make them withstand high voltage, which reduces the cost of manufacturing the electric motor. Additionally, unnecessary power generation and the accompanying core loss are avoided, which reduces the load on the first drive source.
Preferably, the pulley is formed at least the outer peripheral surface of a unitary rotary sleeve, and the field system is arranged directly on the inner surface of the rotary sleeve. The armature is arranged at the center of the rotary sleeve to face the field system, and at least a part of the rotary sleeve is used as electric motor housing.
Accordingly, since no electromagnetic clutch is provided and a single electric motor housing is formed on the inner surface of the pulley with the electric motor arranged in the inside of the housing, the size of the pulley including the electric motor in the inside thereof can be reduced and its weight is also remarkably reduced. Thus, the electric motor can be manufactured at low cost.
Alternatively the field system may be arranged directly on the inner surface of a unitary rotary sleeve, while the armature and the field system are contained in a dedicated motor housing of the electric motor. The electric motor may be bonded to the compressor to be integral with the compressor. Then, a conventional pulley may be used.
Preferably, the field system of the electric motor is formed by using a permanent magnet, and the inner surface of the permanent magnet constitutes a field surface facing the outer peripheral surface of the armature. Then, the electric motor has the form of a simple magneto-type electric motor.
Alternatively, the field system of the electric motor may be formed by using an iron core provided with coils, and the inner surface of the iron core may form a wound field system facing the outer peripheral surface of the armature.
Preferably, the interlocking device is a one-way clutch such that the torque of the first drive source is transmitted from the pulley to the compressor by the one-way clutch when the compressor is driven by the main drive source, and the pulley is allowed to rotate in an advancing direction by the slipping motion of the one-way clutch when the compressor is driven by the electric motor.
Accordingly, when the compressor is driven by the electric motor, the one-way clutch slips so that the pulley and the main drive source are substantially halted.
Preferably, when the compressor is driven by the main drive source and the electric motor is operated, the clutch causes the compressor to rotate with the revolutions per unit time of the pulley plus the revolutions per unit time of the electric motor. Thus, the compressor may be driven to have a high fluid discharging rate, while the compressor itself is relatively small.
Since the complex drive system of the first embodiment is not provided with an electromagnetic clutch, the compressor is constantly driven by the pulley when the main drive source is in operation. Therefore, preferably, the compressor is a variable capacity type compressor in order to make it possible to change the discharging capacity of the compressor independently of the rotational speed of the main drive source.
Alternatively, the compressor may be a fixed capacity type compressor with a clutch located between the pulley and either the armature or the field system to prevent the torque of the pulley from driving the compressor.
Accordingly, it is possible to drive the compressor and stop the compressor at any time it while the main drive source is in operation. Thus the compressor can be operated at the required discharge rate. Thus, the load and the energy consumption of the first drive source are reduced.
Additionally, while a variable capacity type compressor is normally has low efficiency at a reduced discharge rates, a fixed capacity type compressor does not have this problem. Thus, an air conditioning system with a fixed capacity compressor can always be operated efficiently.
Preferably, the electric motor is provided with electric power delivery apparatus to be used for at least either the armature or the field system and the power delivery apparatus is formed by brushes and at least either slip rings or commutators.
The armature of the electric motor can rotate. According to the invention, the field system is supported in such a way that it can also rotate. Therefore, if the electric motor is a commutator type electric motor, not only are commutators and brushes, which make sliding contact with the commutators, located between the field system and the armature, but brushes and the slip rings are located between either the field system or the armature and a stationary part of the compressor.
Thus, two sets of brushes may be needed. Therefore, preferably, when the armature and the rotary sleeve are provided respectively with the commutators and the brush, and when the stationary housing of the compressor is provided with the slip rings, a brush may be located to make sliding contact with both the commutators and the slip rings simultaneously. Accordingly, a single brush operates as two brushes.
The electric motor is not operated when the compressor is driven by the main drive source. However, the sliding contact area of the brush and the slip rings or the commutators in the inside of the electric motor may be unnecessarily worn and power is wasted even when the electric motor is not driven. This problem may be solved by using an arrangement such that, when the compressor is driven by the main drive source by the pulley, the brushes are automatically moved away from the slip rings or the commutators or away from both the slip rings and the commutators.
Preferably, a shaft sealing device for restricting leakage of fluid and lubricating oil from the inside of the compressor is arranged between the pulley and the electric motor.
Accordingly, the inside of the electric motor and that of the compressor can communicate with each other so that, if fluid flowing to the compressor is permitted to flow toward the electric motor, the fluid cools the motor and improves the service life of the electric motor. Alternatively, the size of the electric motor may be reduced at the cost of the extra service life.
Preferably, the first drive source is an internal combustion engine mounted in a vehicle, which is provided with an idle stop control function. Preferably, the compressor is used as the refrigerant compressor of the air conditioning system of the vehicle. Preferably, the power source of the electric motor is a battery mounted in the vehicle.
The parenthesized reference symbols shown above correspond to the specific components of the embodiments described herein.